Objective: Investigations are currently being conducted to evaluate the immunotherapeutic effect of the sulfhydryl inhibitor, iodoacetate in the model AKR mouse lymphoid leukemia. Approach: The immunotherapeutic effects of iodoacetate in this model system are being studied using several criteria. The major emphasis is on an assessment of the agent's effects on cellular and humoral responsiveness. In particular an evaluation of the relative number of T and B cell populations in the thymus, spleen, lymph node and bone marrow of the animals and the functional capabilities of these cell types. Tests presently employed include the use of the cell markers (O, C3 and Ig), PFC response to SRBC, MLR, mitogen responsiveness (PHA, Con A and LPS), GVH capability, serum and cell mediated cytotoxicity towards tumor cells, the effect of the agent on the regulatory T cell and adoptive transfer studies. A study of the effect of iodoacetate on extending the survival of these animals is also included.